/*
 * Created on Feb 27, 2005
 * 
 * Copyright 2005 CafeSip.org 
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); 
 * you may not use this file except in compliance with the License. 
 * You may obtain a copy of the License at 
 *
 *	http://www.apache.org/licenses/LICENSE-2.0 
 *
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * See the License for the specific language governing permissions and 
 * limitations under the License.
 *
 * This class was copied from the Sip Communicator project 
 * (package net.java.sip.communicator.sip.security, its author is 
 * Emil Ivov) and slightly modified here (to remove console/log
 * messages). Thanks for making it publicly available. 
 * It is licensed under the Apache Software License, 
 * Version 1.1 Copyright (c) 2000.
 */

package org.cafesip.sipunit;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * FOR INTERNAL USE, but available to test programs if needed. The class takes
 * standard Http Authentication details and returns a response according to the
 * MD5 algorithm.
 * <p>
 * This class was copied from the Sip Communicator project (package
 * net.java.sip.communicator.sip.security, its author is Emil Ivov) and slightly
 * modified here (to remove console/log messages). Thanks for making it publicly
 * available. It is licensed under the Apache Software License, Version 1.1
 * Copyright (c) 2000.
 * 
 * @author Emil Ivov < emcho@dev.java.net >
 * @version 1.0
 */
public class MessageDigestAlgorithm
{
    /**
     * Calculates a response an http authentication response in accordance with
     * rfc2617.
     * <p>
     * This method was copied from the Sip Communicator project (package
     * net.java.sip.communicator.sip.security, its author is Emil Ivov) and
     * slightly modified here (to remove console/log messages). Thanks for
     * making it publicly available. It is licensed under the Apache Software
     * License, Version 1.1 Copyright (c) 2000.
     * 
     * @param algorithm
     *            MD5 or MD5-sess)
     * @param username_value
     *            username_value (see rfc2617)
     * @param realm_value
     *            realm_value
     * @param passwd
     *            passwd
     * @param nonce_value
     *            nonce_value
     * @param cnonce_value
     *            cnonce_value
     * @param Method
     *            method
     * @param digest_uri_value
     *            uri_value
     * @param entity_body
     *            entity_body
     * @param qop_value
     *            qop
     * @return a digest response as defined in rfc2617
     * @throws NullPointerException
     *             in case of incorrectly null parameters.
     * 
     * 
     */
    public static String calculateResponse(String algorithm,
            String username_value, String realm_value, String passwd,
            String nonce_value, String nc_value, String cnonce_value,
            String Method, String digest_uri_value, String entity_body,
            String qop_value)
    {
        if (username_value == null || realm_value == null || passwd == null
                || Method == null || digest_uri_value == null
                || nonce_value == null)
            throw new NullPointerException(
                    "Null parameter to MessageDigestAlgorithm.calculateResponse()");

        // The following follows closely the algorithm for generating a response
        // digest as specified by rfc2617
        String A1 = null;

        if (algorithm == null || algorithm.trim().length() == 0
                || algorithm.trim().equalsIgnoreCase("MD5"))
        {
            A1 = username_value + ":" + realm_value + ":" + passwd;
        }
        else
        {
            if (cnonce_value == null || cnonce_value.length() == 0)
                throw new NullPointerException(
                        "cnonce_value may not be absent for MD5-Sess algorithm.");

            A1 = H(username_value + ":" + realm_value + ":" + passwd) + ":"
                    + nonce_value + ":" + cnonce_value;
        }

        String A2 = null;
        if (qop_value == null || qop_value.trim().length() == 0
                || qop_value.trim().equalsIgnoreCase("auth"))
        {
            A2 = Method + ":" + digest_uri_value;
        }
        else
        {
            if (entity_body == null)
                entity_body = "";
            A2 = Method + ":" + digest_uri_value + ":" + H(entity_body);
        }

        String request_digest = null;
        if (cnonce_value != null && qop_value != null
                && (qop_value.equals("auth") || (qop_value.equals("auth-int"))))
        {
            request_digest = KD(H(A1), nonce_value + ":" + nc_value + ":"
                    + cnonce_value + ":" + qop_value + ":" + H(A2));

        }
        else
        {
            request_digest = KD(H(A1), nonce_value + ":" + H(A2));
        }

        return request_digest;
    }

    /**
     * Defined in rfc 2617 as H(data) = MD5(data);
     * 
     * @param data
     *            data
     * @return MD5(data)
     */
    private static String H(String data)
    {
        try
        {
            MessageDigest digest = MessageDigest.getInstance("MD5");

            return toHexString(digest.digest(data.getBytes()));
        }
        catch (NoSuchAlgorithmException ex)
        {
            // shouldn't happen
            return null;
        }
    }

    /**
     * Defined in rfc 2617 as KD(secret, data) = H(concat(secret, ":", data))
     * 
     * @param data
     *            data
     * @param secret
     *            secret
     * @return H(concat(secret, ":", data));
     */
    private static String KD(String secret, String data)
    {
        return H(secret + ":" + data);
    }

    // the following code was copied from the NIST-SIP instant
    // messenger (its author is Olivier Deruelle). Thanks for making it public!
    /**
     * to hex converter
     */
    private static final char[] toHex = { '0', '1', '2', '3', '4', '5', '6',
            '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

    /**
     * Converts b[] to hex string.
     * 
     * @param b
     *            the bte array to convert
     * @return a Hex representation of b.
     */
    private static String toHexString(byte b[])
    {
        int pos = 0;
        char[] c = new char[b.length * 2];
        for (int i = 0; i < b.length; i++)
        {
            c[pos++] = toHex[(b[i] >> 4) & 0x0F];
            c[pos++] = toHex[b[i] & 0x0f];
        }
        return new String(c);
    }

}